In internal combustion engine control units there are diagnosis functions capable of detecting a malfunction of the individual pressure sensors. In systems having two pressure sensors, the known diagnosis functions may provide an incorrect diagnosis, e.g., identify the wrong sensor as being defective, which may result, for example, in replacement of an error-free sensor.
Misdiagnosis of a supposedly defective sensor results in the error-free sensor, rather than the defective sensor, being classified as defective, and possibly replaced, for example, in a workshop. This results furthermore in the vehicle possibly returning to the workshop for actually needed repairs, causing increased costs, because error-free sensors were previously replaced and now the defective sensor will need to be replaced.
An object of the present invention is therefore to be able to unambiguously detect a defective intake-manifold pressure sensor or a defective ambient-pressure sensor.